Art of cracking hydrocarbons



@da 29y E929.. E. c. HERTHEL. ET A1..

ART OF CRACKING HYDROCARBONS Filed June l1, 1927 @lung Patented Oct. 29,1929 UNITED 'STATES PATENT .oi-Fica EUGENE C. HERTHEL, OF CHICAGO,ILLINOIS, AND

HARRY L. rnLzEn, or HIGHLAND,

INDIANA, ASSIGNORS-TO SINCLAIR BEFINING COMPANY, OF NEW' YORK, N. Y., A

CORPORATION OF MAINE ART OF ORACKING HYDROCARBONS Application filed June11,

to form on the heated surfaces ot' the still,`

necessitating the shut down of the still for cleaning between successiveruns. ll`he shutting down of a pressure still, the Withdrawal of thecharge therefrom, the cleaning of the still, the recharging of the stilland the preliminary heating of the still to bring the fresh charge up tocracking conditions, all

i requiretime, and the total amount of time usually required in ordinarycommercial operations means a corresponding reduction 1n the proportionof time during which thestill is operating for carrying out the desiredcracking operation. llhis invention provides forl greater continuity ofoperation, less loss of time, and greater production per still per day.

When a pressure still is charged with gas oil or other charging stocksto be cracked, and the charge heated to a cracking tempera.- ture, thecracking takes place in a gradual and progressive manner. The lighterconstituents produced by the cracking operatiom which go to make up thepressure distillate',

40 ai'e removed from the still progressively during the crackingoperation. Other constituents, such as heavier hydrocarbons formed bythe cracking operation, may remain and mix with the charge in the still.There is. also aprogressive formation of asphaltic or pitchlikeconstituents. For the most part, these constituents remain in solutionin the charge during the first part of the run, and they may remaincompletely in solution in the first part of the run. As the crackingoperation convlarly objectionable character, the foi-mation 1927. SerialNo. 198,249.

tinues, however, the amount of such asphaltic or pitch-like constituentsgradually and progressively increases until, sooner or later, the amountof such constituents exceeds the Vsaturation point.

These asphaltic or pitch-like constituents appearto be of varyingproperties and charatteristics. With the exception of certain of theseconstituents which are of particuof coke or carbonaceous deposits uponthe heated surfaces of the still is largely avoided so long as theseasphaltic or pitch-like constituents are kept in solution in the chargeof oil in the pressure still. Certain of these constituents, whichappear to be relatively small in amount as coin pared with the totalamount of the asphaltic or pitch-like constituents formed, however, areapparently'of a different character and seein to have an increasedtendency to deposit on the heated surfaces of the still. Among theheavier constituents produced by the cracking operation which seem to beparticularly objectionable are certain sulpliur-containing compounds.With charging stocks which contain sulphur, some of the sulphurcompounds appear to undergo cracking to form sulphur-containingconstituents, of an asphaltic or pitch-like character, -which areparticularly objectionable. Analyses of the deposits 0n the heatedsurfaces of pressure cracking stills indicate that certain. of thesesulphur-containing constituents have a preferential aiinity for theheated surfaces, or'tend to separate out on such surfaces, foriningdeposits containing bothiron and sulphur in .pro ortions approximatingthose of iron sulplii e. It is also possible that asphaltic orpitch-like constituents of a colloidal charactei', or even colloidalcarbon, formed as a result ofthe crackig operation, tend to separate outon the heating surfacesl of the pressure still in a preferential manner.

In carrying out the present invention, both the nature and the amount ofthe as haltic orl pitch-like constituents formed in t e charge of oilinthe pressure still as the cracking operation continues are regulatedand controlled; certain of these constituents are selectively removedfrom the still charge by 100 maintaining within and directly exposed tothe still charge a body of fullers earth or similar absorbent materialand the amount of asphaltic and pitch-like constituents remaining in thestill charge by the discharge of pitchladen oil from and the supply ofraw oil to the still charge during the cracking operation. The body offullers earth maintained within and directly exposed to the stillcharge, is arranged to permit free circulation of the oil in the still.This body of fullers earth does not remove from the still charge all ofthe asphaltic or pitch-like constituents; but it seems to have aselective action upon certain of these constituents, and apparentlyremoves those constituents which are particularly objectionable from thestandpoint ofcausing or promoting the formation of coky or carbonaceousdeposits on the heated surfaces of the still. This action of the fullersearth seems to be due in part at least to a selective desulphurizingaction of the fullers earth upon the pressure still charge wherebycertain of the more `objectionable sulphur-containing constituents ofthe charge are selectively removed. 'lhe invention thus provides for theremoval of more objectionable pitch-like or asphaltic constituentsfromthe pressure still charge by the action of the fullers earth or similarabsorbent material and at the same time for regulation of the content ofless objectionable ashaltic or pitch-like constituents remaining 1n thestill charge by the supply of raw oil and the discharge of itch-ladenoil. The

supply of raw oil and t ie discharge of pitchto maintain theconcentration of asphaltic or itch-like constituents in the still chargebeow saturation.

The invention'will be further described in .connection with theaccompanying drawings,

which illustrate, in a solnewhat conventional and diagrammatic manner,one form of pressure still adapted for the practice of the process ofthe invention; but it is intended and will be understood that theinvention is not limited to operations carried, out in the specificconstruction used for the purpose of illustration. In the accompanyingdraw- 111 S2 ig. 1 represents, in elevation and partly in section andwith parts broken away, a

pressure still adapted for carrying out the process of the invention,Fig. 2 is a sectional lview of the bulk supply drum of the stillillustrated in Fig. 1, and Figs. 3 and 4 are enlarged fragmentarysectional views of forms of screenssuitable for retainingr the fullersearthor other absorbent material.

The pressure still illustrated comprises a bulk supply drum 1 and abattery of heating tubes 2 arranged in a heating furnace and circulatingconnections 3, 4 and 5 including' a circulating pump 6 to provide forcirculation of oil from the bulk supply drum upwardly through theheating tubes and back to the bulk supply drum. The heating furnacecomprises a tirebox 7 in which fuel is burned for supplying heat to thecracking operation connected to the upper end of a heating flue in whichthe heating tubes 2 are arranged. The lower end of this heating flue isconnected to a stack flue 8. A return flue 9, provided with suitableforcing means, is arranged for recirculating part of the heating gasesescaping from the lower end of the heating flue again through theheating flue in admixture with fresh hot products of combustion from theirebox for tempering, in an advantageous manner, the heating gasespassing over the heating tubes. A retlux tower 10 is arranged above thebulk`supply drum 1 and connected thereto by a vapor line 1l and a returnline 12. This return line 12 is arranged to discharge into the upper endof the circulating connection 3. Vapors from the reflux tower passthrough the vapor line 13 to the condenser 14 arranged to discharge intothe receiver 15. Connection 16 is provided for discharging thedistillate product and connection 17 for discharging uncondensed vaporsand gases from the receiver 15. The pressure in the system may bemaintained and regulated by means of valve 18, or by suitable valvesarranged beyond the condenser. Connection 19 is provided for dischargeof tar or pitchladen oil from the pressure still during operation.Connection 20 is provided for pumping out the still at the end of a runand for initially charging the still at the beginning of a run. Feedline 21is provided for supplying raw oil during operation. Cool raw oilmay also be supplied through connection 22 in amount just sullicient tocool and lubricate the bearings of the circulating pump 6, or an amountof raw oil considerably in excess of this amount may be sur `iliedthrough connection 22 during operation.

A basket 23 is arranged within the bulk supply drum of the pressurestill and below the normal liquid level therein. This basket is ofconstruction adapted to permit free passage of oil therethrough yet toretain within the basket a body of finely divided fullers earth orsimilar absorbent material. For example, it may be made up of one ormore7 screens of graduated fineness adapted to retain the fullers earthor similar absorbent material arranged between perforated supportingplates, as illustrated in Figs. 3 and 4. This basket is supported in thebulk supply drum free from the sides of the drum so as to permit freecirculation of oil through the bulk supply drum from the heating tubesand back to the heating tubes and to provide open liquid paths throughthe bulk supply drum between the return connections from to the heatingtubes. In operation, a body of ullers earth or the like 24 is maintainedin this basket. In a pressure still in which the operating chargeamounts to something in the neighborhood of 10,000 gallons, this body ofullers earth may amount to four or five tons. It is advantageous to userelatively coarse fullers earth, say from l5 to 30 mesh. In place offullers earth, other absorbent clays and the like, particularly thosewhich have desulphurizing capacity, are also useful in carrying out theinvention. One or more screens may also be arranged on top of the bodyof fullers earth or the like in the basket 23 to reduce any tendency ofthe oil circulating through the bulk supply drum to disturb the body offullers earth or the like.

In carrying out the present invention inthe apparatus illustrated, thepressure still is charged with fresh charging stock in the usual Way.The charging stock may be, for example, gas oil or other suitablecharging stock which is to be cracked for the production of gasoline ora gasoline-containing pressure distillate. Due to the selective orpret'- erential action ofthe body of fullers earth or the like, it ispossible to treat charging stocks containing constituents whichotherwise would tend to cause 'excessive deposition of coky orcarbonaceous material. The still charge is brought to the requiredcracking temperature and pressure in the usual manner. For theproduction of .gas-

l oline or a gasoline-containing pressure distillate from gas oil, forexample, pressures up to 125 pounds per square inch or higher pressuresmay be used. After the cracking temperature is reached, cracking beginsand takes place in a gradual and progressive manner, the lighter vaporsforming the pressure distillate escaping to the condenser while heaviervapors are reiuxed and returned to the still from the retiux tower. Thecharacter of the distillate product may be controlled by regulating therate at which raw oil is supplied to the reflux tower. The moreobjectionable constituents formed in the cracking operation areselectively removed by the body ot' fullers earth or the like, and,before the amount of asphaltic and pitch-like constituents accumulatingin the still charge reach the saturation point, the discharge of tar orpitch-laden oil is be un, and the rate at which raw oil is supphed andthe rate at which tar is discharged are conjointly regulated to maintainthe concentration of asphaltic or pitch-like constituents in thecirculating charge below objectionable values, advantageously below thesaturation point.

The circulating charge is thus ke t of a regulated pitch content whileit is a so subjected to the selective action of the fullers earth orsimilar absorbent material. While the body of fuller-s earth iscompletely submerged or immersed in the charge of oil in the still sothat it is directly exposed thereto and so that a maximum area of theearth is exposed to a maximum proportion of the still charge, the bodyof earth is arranged, in carrying out this invention, to permit freecirculation through the bulk supply drum in which the body of earth isarranged of the still charge recirculating through the heating tubes.Due to the selective action of the body of fullers earth or similarabsorbent material in removing the more objectionable constituentsformed by the cracking operation,

a larger proportion of the raw oil. supplied to the operation can betaken ofi as distillate and asmaller proportion discharged as pitchladenoil than in an otherwise similar operation in which the body of fullersearth or the like is not used. This makes possible an increase in stillcapacity as Well as a saving in fuel.

Fullers earth is a particularly advantageous material for use in theprocess of the invention. It appears to combine in itselil valuableabsorbent desulphurizing and other properties which favorably affect andbenefit the pressure still operation.

We claim:

l. An improved method of cracking hythrough heating tubes and back tothe bulk supply drum and heating it to a cracking temperature in theheating tubes, taking otf vapors including vapors of the cracked productfrom the bulk supplyy drum under pressure, maintaining within the chargeof oil in the bulk supply drum belovi1 the normal liquid level thereinand directly exposed to the oil therein a body of fuller-s earth, saidbody of fullers earth being arranged to permit free circulationy of oiland to provide open liquid paths through the bulk supply drum from andto the heating tubes, circulating oil supplied from the heating tubes tothe bulk supply drum in part directly through said body of fullers earthand back to the heating tubes and in part through said open liquid pathsand back ,f to the heating tubes. and sup lying` raw oil to anddischarging pitch-la en oil from the char e of oil in the pressure stillduring the disti ation.

2. An improved method of cracking hydrocarbon oils by distillation underpressure, which comprises circulating a charge of oil in a pressurestill from a bulk suppl drum through heating tubes and bac-k to tie bulksupply drum and heating it to a crackinff' temperature in the heatintubes, taking o vapors including vapors o the cracked product from thebulk supply drum under pressure, maintaining within the charge of oil inthe bulk supply drum below the normal liquid level therein and directlyexposed to lll) the oil therein a body of desulphurizing mal terial,said body of desulphurizing material being arranged to permit freecirculation of oil and to provide open liquid paths through the bulksupply drum from and to the heating tubes, circulating oil supplied fromthe heating tubes to the bulk supply drum in part directly through saidbody of desulphurizing material and back to the heating tubes and inpart through said open liquid paths and back to the heating. tubes, andsup lying raw oil to and discharging pitch-ladlen oil from the charge ofoil in the pressure still dui-iner the distillation.

3. n improved method of cracking hydrocarbon oils by distillation underpressure, which comprises circulating a charge of oil in a pressurestill from a bulk supply drum through heating tubes and back to the bulksupply drum and heating it to a cracking temperature in the heatingtubes, taking off vapors including vapors of the cracked product fromthe bulk supply drum under pressure, maintaining-Within the charge ofoil in the bulk lsupply drum below the normal liquid level therein anddirectly exposed to the oil therein a body of fullers earth, said bodyof fullers earth being arranged to permit free circulationof oil and toprovide open liquid paths through the bulk supply drum from and to theheating tubes, circulating oil supplied from the heating tubes to thebulk supply drum in part directly through said body ot fullers earth andback to the heating tubes and in part through saidv open liquid pathsand back to the heating tubes, supplying raw oil to and dischargingpitch-laden oil from the charge of oil in the pressure still during thedistillation, and conjointly regulating the supply of raw oil anddischarge ot' pitch-laden oil to maintain the pitch concentration in thecharge of oil below saturation.

4. An improved method of cracking hydrocarbon oils by distillation underpressure, which comprises circulating a charge of oil in a pressurestill from a bulk supply drum through heating tubes and back to the bulksupplydrum and heating it to a cracking `temperature in the heatinrrtubes, taking oit' vapors including vapors of the cracked product fromthe bulk supply drum under pressure, maintaining Within the charge ofoil in the bulk supply drum below the normal liquid level therein anddirectly exposed to the oil therein a body of desulphurizing material,said body of desulphurizing material being arranged to permit freecirculation ot oil and to provide open liquid paths through the bulksupply drum from and to the heatin(ir tubes, circulating oil suppliedfrom the lieating tubes to the bulk su )ply drum in part direct- 1ythrough said body of desulphurizing ma- 'terial and back to the heatingtubes and in part through said open liquid paths and back to the heatingtubes, supplying raw oil to and discharging pitch-laden oil from thecharge' of oil in the pressure still during the distillation, andconjointly regulating the supply of raw oil and discharge of pitch-ladenoil to maintain the pitch concentration in the charge of oil belowsaturation.

-An improved method of cracking hydrocarbon oils by distillation underpressure, which comprises circulating a charge of oil in a pressurestill from a bulk supply drum through heating tubes and back to the bulksupply drum and heating it to a crackin temperature in the heatin tubes,taking o vapors including vapors ot the cracked product from the bulksupply drum under pressure, maintaining within the charge of oil in thebulk supply drum below the normal liquid level therein and directlyexposed to the oil therein a body of solid absorbent material, said bodyof solid absorbent material being arranged to permit free circulation ofoil and to provide open liquid paths through the bulk supply drum fromand to the heating tubes, circulating oil supplied from the heatingtubes to the bulk supply drum in part directly through said solidabsorbent material and back to the heating tubes and in part throughsaid open liquid paths and back to the heating tubes, and supplying rawoil to and discharging pitch-laden oil from the charge of oil in thepressure still during tl'iedistillation.

EUGENE C. HERTHEL. HARRY L. PELZER.

